The present invention generally relates to energy conversion compositions, excluding conversion of electrical energy into mechanical energy, which can effectively absorb and damp energy such as dynamic, thermal, and/or electrical energy excluding optical energy.
There conventionally exists a vibration energy damping material of a soft vinyl chloride resin and a plasticizer.
Such a soft vinyl chloride resin can damp vibration energy on the surface of and/or within the resin by converting the vibration energy into frictional heat, only to a very limited extent.
Japanese Laid-Open Patent Publication No. 5-332047 discloses a liquid material which absorbs or damps vibration energy to a degree. This liquid material or a viscous fluid comprises a glycol as a chief ingredient. Vibration energy or seismic energy generates an electric field in the viscous fluid and changes the viscosity of the fluid, an attempt to efficiently damp the dynamic energy.
A very large amount of liquid material is required to effectively damp huge seismic energy, for instance, from a major earthquake. Due to gradual oxidization of the liquid material, its damping performance gets lowered over time, requiring periodical refreshment of the liquid material. Accordingly, there exists a strong demand for a vibration damping material which with a minimum amount can efficiently damp seismic energy or vibrations over a longer period of time without such refreshment.
A sound or noise absorptive or damping material containing glass wool is known. Glass wool can damp sound or noise by consuming the energy as frictional heat when sound collides with the surface of glass wool fibers and passes therethrough.
The glass wool type sound absorptive material, however, need be prepared relatively thick to provide sufficient sound absorption. The material cannot effectively absorb sound of a low frequency below 1,000 Hz. The material does not function well at a frequency below 500 Hz.
There is an impact absorptive or damping material. Japanese Patent Laid-Open Publication No. 6-300071 discloses an impact absorptive material which comprises short fibers dispersed in a foamed polymer. This impact absorptive material can damp an impact applied against a surface portion of the formed material through the gradual collapse of the structural integration of the formed material. The short fibers dispersed in the foamed material act as a physical binder to promote the tensile strength of the material and prevent its cracking.
This impact absorptive material, however, requires a considerable thickness and volume to provide sufficient impact damping. Accordingly, if there is no sufficient room for installment, this impact absorptive material cannot be conveniently utilized.
There is an electromagnetic shield material as proposed in Japanese Patent Laid-Open Publication No. 5-255521, which can absorb electromagnetic energy to an extent. This material comprises an ultraviolet absorptive compound capable of absorbing or damping ultraviolet rays of a wavelength of 250 to 400 nm through excitation of the molecules of the compound and conversion of the ray energy into thermal energy.
This material need be 10 to 20 mm thick to provide a sufficient absorption of ultraviolet rays. Such a thick sheet hinders visibility. A demand for a material which can provide a thin but effective electromagnetic shield is strong.
Butyl rubber or NBR is conventionally utilized to provide a vibration damping material. Such a rubber material is economical and easy to process as well as possesses a considerable mechanical strength.
Such a rubber material shows an excelled vibration damping property among polymers, however, if a rubber material is used singly, its damping ability is somehow limited. Therefore, a metal plate or core or oil damper is conventionally incorporated in a rubber-type vibration damping material, which is rather complicated and costly to manufacture.
Accordingly, there is a strong demand for a vibration damping material which itself can provide excellent vibration absorption or damping.
Japanese Patent Laid-Open Publication No. 5-5215 discloses an endothermic fiber material. This material is a polymer comprising a straight-chain aliphatic carboxylic acid and straight-chain aliphatic diol, such as polyethyleneadipate, polypentamethyleneadipate, or polytetramethynenglutarate. The polymer absorbs heat as it melts and provides heat damping, though, a large amount of polymer is required to provide sufficient heat absorption.
A viscous fluid mainly composed of a glycol provides a high latent heat medium to be used as a transmission cooler, engine coolant or mold cooler. The cooling property of the fluid is given by the following equation.
(xcex94Hxe2x88x92RT)/V=(SP)2 
xcex94H: latent heat, SP: SP value (solubility parameter). The SP value is an indication of polarity and increases as dipoles increase. Water has the largest SP value, however, use of water is not practical because water tends to corrode metals. Glycol has an excellent rust inhibition property, however, glycol does not provide a high latent heat property.
As described above, conventional energy conversion (damping) materials or compositions have insufficient damping capabilities, or require a considerable thickness or volume to provide a satisfactory damping capability.
The inventors have discovered through a lengthy research on energy conversion compositions that the magnitude of dipole moment of the compositions is directly related to their energy absorption/conversion/damping capability.
The inventors have also found that the dielectric loss factor of the compositions is related with their energy absorption/conversion damping capability.
Accordingly, an object of the present invention is to provide an energy conversion composition, excluding conversion of electrical energy into mechanical energy, which has an excellently improved capability of absorbing/converting or damping energy such as dynamic, thermal, and/or electric energy excluding optical energy. Another object, of the present invention is to provide an energy conversion/damping composition which can provide an excellently improved ability with a minimal thickness or volume.
An energy conversion composition according to this invention can be prepared into, but not limited to, an unconstrained or constrained vibration damping sheet, paint, paper, asphalt material (for automobile flooring), or a vibration damping material for asphalt roads (noiseless roads), or sound or noise absorptive material for sound absorptive sheets, fibers, foam materials, films or molds, or impact absorptive material for training shoe soles, protections, head gears, plaster casts, mats, supporters, handle grips and saddles of bicycles or motorbikes, front forks, grip ends of tennis or badminton rackets, baseball bats, or golf clubs, grip tapes, hammer grips, slippers, gun bottoms, shoulder pads, or bulletproof jackets, or vibration-proof rubber material for earthquake damping rubbers or molds, or electromagnetic shield material for X-ray or ultraviolet shield sheets, or piezoelectric material (excluding ones that convert electrical energy to mechanical energy), or endothermic material for endothermic fibers or pellets, or viscous fluid for earthquake damping apparatus, or polarity liquid for engine mount liquids, shock absorber oils, power supply transmission cooling liquids, engine coolants, floor heater media or solar heat media.
The energy conversion composition according to this invention is characterized in that its base material contains a moment promoter or moment activator which increases or promotes the amount or magnitude of dipole moment in the base material.
Such a base material is not limited to but may be a polymer material such as polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, polyvinylidene fluoride, polyisoprene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), or their selected mixture, among which polyvinyl chloride is preferred for its workability and low cost.
When such an energy conversion composition is to be made into a noise or impact absorptive material, electromagnetic shield material, endothermic material, or polarity material, its base material may be additionally provided with polyester, polyurethane, polyamide, polyvinylidene, polyacrylonitrile, polyvinylalcohol, or cellulose. In particular, when the composition is to be made into a sound absorptive material, a foaming agent may be added to provide a porous material to improve sound damping.
When the composition is to be made into a vibration damping rubber material, the base material may be acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), or isoprene rubber (IR). When a polarity liquid is to be provided, the base material may be a glycol or water.
Mica scales, glass pieces, carbon fibers, calcium carbonate, barite, precipitated barium sulfate, corrosion inhibitor, dye, antioxidant, electricity control agent, stabilizer, or wetting agent may be selectively added to the base material as desired.
When vibration, sound, impact, electricity, pressure, or heat energy is applied onto the base material, dipoles 12 in the base material 11 as shown FIG. 1 are displaced to a state such as shown in FIG. 2. This displacement of the dipoles 12 may be caused by rotation or shifting of phase within the base material 11.
Prior to application of energy, the dipoles 12 in the base material 11 as shown in FIG. 1 are stable. When an energy is applied onto the base material, the dipoles 12 in the base material 11 are displaced into an unstable state. They are then prompted to return to a stable state such as shown in FIG. 1.
The applied energy is effectively consumed through this process. It is assumed that the consumption of energy provided by the displacement and recovery of the dipoles provides noise, impact, vibration, electromagnetic wave, or heat damping.
The mechanism of energy absorption/damping is associated with the magnitude of dipole moment in the base material 11. When the magnitude of dipole moment in the base material 11 is large, the base material 11 possesses a high energy absorptive capability.
The magnitude of dipole moment in the base material is subject to the base material used. Even when the base material is the same, the magnitude of dipole moment to be provided in the base material varies with the working temperature. The magnitude of dipole moment is also affected by the type and magnitude of particular energy applied onto the base material. Thus, the base material should be selected so as to provide the largest possible magnitude of dipole moment, considering the possible or expected working temperature as well as the type and magnitude of the energy to be applied.
It is desirable to also take into consideration factors such as workability, availability, temperature characteristics (temperature resistance), weatherability, and price of the base material in selecting the base material ingredient or ingredients.
A moment activator is blended in the base material to significantly increase the magnitude of dipole moment of the base material.
The moment activator itself may or may not provide a large magnitude of dipole moment, however, in combination with the base material it can significantly promote the overall magnitude of dipole moment in the base material.
The magnitude of dipole moment in the base material 11 will be increased by three to ten times under the same temperature and energy conditions as exemplary shown in FIG. 3 by blending a moment activator therein. The consumption of energy provided by the recovery of the dipoles in the base material is unexpectedly great, providing an unexpectedly improved total energy absorption/damping capability.
The moment activator which can provide such an unexpected effect may be a compound or compounds having a benzothiazyl radical such as N,N-dicyclohexylbenzothiazyl-2-sulfenamide (DCHBSA), 2-mercaptobenzothiazole (MBT), dibenzothiazylsulfide (MBTS), N-cyclohexylbenzothiazyl-2-sulfenamide (CBS), N-tert-butylbenzpthiazyl-2-sulfenamide (BBS), N-oxydiethylenebenzothiazyl-2sulfenamide (OBS), or N,N-diisopropylbenzothiazyl-2-sulfenamide (DPBS), or a benzotriazyl radical such as 2-2xe2x80x2-hydroxy-3xe2x80x2-(3xe2x80x3, 4xe2x80x3, 5xe2x80x3, 6xe2x80x3 tetrahydrophthalimidemethyl)-5xe2x80x2-methylphenyl)-benzotriazole (2HPMMB), 2-2xe2x80x2-hydroxy-5xe2x80x2 methylphenyl)-benzotriazole (2HMPB), 2-2xe2x80x2-hydroxy-3xe2x80x2, 5xe2x80x2-di-t-butyl--5xe2x80x2-methylphenyl)-5-chlorobenzotriazole (2HBMPCB), 2-2xe2x80x2-hydroxy-3xe2x80x2, 5xe2x80x2-di-t-butylphenyl)-5-chlorobenzotriazole (2HDBPCB) having as a nucleus benzotriazole comprising an azole radical bound to a benzene ring, to which a phenyl radical is bound, or a diphenylacrylate such as ethyl-2-cyano-3,3-di-phenylacrylate (ECDPA).
Moment activators have their own dipole moment. The magnitude of dipole moment in a base material containing a moment activator is subject to the working temperature as well as the type and magnitude of energy applied to the base material. Accordingly, a moment activator to be blended in a base material should be selected so as to provide the largest possible magnitude of dipole moment in the base material, considering the working temperature and the type and magnitude of energy to be applied. When a polymer material is used as the base material for a vibration damping or sound absorptive material, it is important to select a moment activator to be blended in the base material considering the compatibility of both, or their respective SP values, which should advantageously be close for a better miscibility.
An energy conversion product according to this invention can be provided by blending a selected base material and selected moment activator and optionally additives such as a filler or dye, and molding or spinning the mixture into a film, fibrous or block material. Conventional blending and molding or spinning means can be utilized.